Vertical gas induced flotation cell

Abstract

A system for separating oil and/or oily coated solids from an oily water mixture. The system includes an upright vessel having an inlet for introducing oily water in a horizontal pattern. The vessel also has a water outlet in a lower portion of the vessel and an oil outlet. An eductor is positioned within a lower portion of the vessel and is arranged to disseminates small gas bubbles in a radial, substantially horizontal pattern and substantially uniformly over the full cross-sectional area of the vessel. The bubbles migrate upwardly against the downward flow of oily water within the vessel and attach to oil droplets and/or oily coated solids augmenting the buoyancy thereof, and thereby enhancing oily contaminant separation from water. A two-stage oil skimmer bucket is located in a top portion of the vessel by which separated oil is collected and discharged through the oil outlet.

1. A method of separating oil and/or oily coated solids from a gaseous oily water mixture in an upright vessel having an inlet for introducing gaseous oily water mixture into an upper portion of the vessel, a water outlet in a lower portion of the vessel and an oil outlet, comprising the steps of:
 (a) flowing the gaseous oily water mixture from said vessel inlet tangentially into an upright tubular cyclonic inlet member positioned concentrically within an upper portion of said vessel; 
 (b) extracting by cyclonic action, large gas bubbles without extracting small gas bubbles and discharging the inlet mixture of oily water and small gas bubbles in a substantially horizontal pattern to disperse the oily water mixture over substantially all the full cross-sectional area of said vessel; 
 (c) flowing pressurized water through an eductor positioned within a lower portion of said vessel, the eductor having a gas inlet connected to a source of gas and an outlet through which ejected water having small gas bubbles entrained therein passes; 
 (d) disseminating the ejected water and entrained gas bubbles in a radial substantially horizontal pattern that uniformly disperses the small gas bubbles over substantially the full cross-sectional area of said vessel, the small gas bubbles migrating upwardly to adhere to and add buoyancy to oil and/or oily coated solids; 
 (e) skimming separated oil and/or oily coated solids in a top portion of said vessel; and 
 (f) discharging the separated oil and/or oily coated solids through said oil outlet. 
 
     
     
       2. A method according to  claim 1 , including the step of passing the inlet mixture through a coalescing section positioned between said vessel inlet and said water outlet to promote oil droplet coalescence. 
     
     
       3. A method according to  claim 1  in which the step of passing the inlet mixture through a coalescing section includes passing the inlet mixture through a horizontal layer of spaced apart oleophylic elements. 
     
     
       4. A method according to  claim 1  wherein gas extracted by said cyclonic inlet member collects within an upper interior portion of said vessel and including the step of passing gas by way of a pipe extending from the vessel upper interior portion to said eductor gas inlet thereby providing said source of gas. 
     
     
       5. A method according to  claim 1  including the step of employing a water pump having an inlet in communication with said vessel water outlet and an outlet in communication with said eductor inlet providing said source of pressurized water. 
     
     
       6. A method according to  claim 1  including the step of providing pressurized water by means of a pump having an inlet connected to said vessel water outlet and the step of providing a source of gas in the form of a pipe connected to an upper interior portion of said vessel whereby water and gas employed in said eductor are both recycled from within said vessel interior. 
     
     
       7. A method according to  claim 1  including the step of providing an eductor in the form of a venturi body having a venturi-forming passageway there through connected at one end to said source of pressurized water, the venturi body having a laterally extending gas inlet opening communicating with said venturi-forming passageway and an eductor outlet end surface that receives said venturi-forming passageway and including the step of horizontally deflecting water from said eductor outlet by which water and small gas bubbles are distributed radially and horizontally into said vessel interior. 
     
     
       8. A method according to  claim 1  wherein the step of skimming separated oil and/or oily coated solids includes the use of a two-stage skim bucket. 
     
     
       9. A method of separating oil and/or oily coated solids from an oily water mixture in an upright vessel, including the steps of:
 flowing the oily water mixture tangentially into an upright cyclone inlet member positioned concentrically within an upper portion of the vessel and extracting by cyclonic action large gas bubbles without extracting small gas bubbles from the mixture; 
 deflecting the oily water mixture containing said small gas bubbles from said cyclone inlet member in a horizontal pattern over substantially the full cross-sectional area of an upper portion of the vessel; 
 pumping water under pressure through an eductor having a source of gas to provide water having small gas bubbles infused therein; 
 distributing water having small gas bubbles infused therein from the eductor in a substantially horizontal pattern over substantially the full cross-section area of a lower portion of the vessel, bubbles from the water migrating upwardly and attaching to oil droplets and oily coated solids augmenting the buoyancy thereof, enhancing oil and oily coated solids separation; and 
 withdrawing oil and oily coated solids from an upper portion and cleaned water from a lower portion of the vessel. 
 
     
     
       10. A method of separating oil and/or oily coated solids from an oily water mixture according to  claim 9  wherein said vessel has a water collecting area in a lower portion therein and including the step of extracting water from said vessel lower portion to provide water as employed in step (b). 
     
     
       11. A method of separating oil and/or oily coated solids from an oily water mixture according to  claim 9  including the step of skimming oil and oily coated solids from an upper portion of the vessel employing a two stage skim bucket. 
     
     
       12. A method of separating oil and/or oily water coated solids from an oily water mixture according to  claim 9  including the steps of passing both the down flowing oily water mixture and the upwardly migrating bubbles through a coalescing section formed by a horizontal layer of oleophylic elements. 
     
     
       13. A method according to  claim 9  wherein the oily water mixture has an average vertically downward flow velocity of about two feet per minute. 
     
     
       14. A method according to  claim 9  wherein the step of discharging the inlet mixture in a substantially horizontal pattern includes discharging the inlet mixture with a cyclonic motion in an upper portion of the vessel. 
     
     
       15. A method according to  claim 9  wherein a substantial portion of said small gas bubbles entrained in the water ejected from said eductor are of about 100 to 500 microns in initial diameter. 
     
     
       16. A method according to  claim 9  in which said eductor introduces gas in the form of bubbles into said oily water mixture at a rate of about 0.3 to 3.0 standard cubic feet of gas per barrel of oily water passing into said vessel. 
     
     
       17. A method according to  claim 9  in which said eductor introduces gas in the form of bubbles into said oily water mixture at a rate of about 0.5 to 1.0 standard cubic feet of gas per barrel of oily water passing into said vessel.